Experimental and numerical study of initial water mobility in bitumen reservoirs and its effect on SAGD

Interstitial water in a water-wet bitumen reservoir can form a continuous water network, which allows reservoir water to flow throughout the reservoir. A primary objective of the paper was to develop an experimental method to measure the water effective permeability of the continuous water network in an unconventional oil–water system. In experiments, semi-permeable membranes were installed at the production end of sandpacks to create a stationary oil phase condition. Experimental results showed that the water phase could flow under low permeability at initial water saturations. A cylindrical capillary tube model was developed to analyze experimental results and it showed that different wetting film thicknesses inside a porous medium could alter the overall effective permeability under the same initial water saturation. In the case study, different reservoir simulation operations were performed to compare influences of initial water movement. It was concluded that, under a small amount of initial water movement across the boundary, the pressure profiles and flow patterns of reservoir water changed.

► Initial water mobility is determined under immobile oil condition. ► Irreducible water saturations in bitumen reservoirs are much lower than the connate saturations. ► Initial water movement depends on the continuity of the water network in thin film. ► Water movement under initial reservoir conditions dissipates pressure of SAGD operations.